tutor-bounces+christopher.henk=allisontransmission....@python.org wrote on 09/10/2009 04:13:23 PM:
> I'm not sure why I'm getting an error at the end here: > > >>> class dummy: > ... def __init__(self,dur=0): > ... self.dur=dur > ... > >>> z=dummy(3) > >>> z.dur > 3 > >>> z=dummy(dur=3) > >>> z.dur > 3 > > That worked fine, of course. > > >>> class dummy2(str): > ... def __init__(self,dur=0): > ... self.dur=dur > ... > >>> z=dummy2(3) > >>> z.dur > 3 > > So far so good. But: > > >>> z=dummy2(dur=3) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: 'dur' is an invalid keyword argument for this function > >>> > > Why doesn't that last bit work? I'm not sure where to begin to look > this up. > Thanks! > > -- > -dave---------------------------------------------------------------- > "Pseudo-colored pictures of a person's brain lighting up are > undoubtedly more persuasive than a pattern of squiggles produced by a > polygraph. That could be a big problem if the goal is to get to the > truth." -Dr. Steven Hyman, Harvard > I believe it has to do with the fact that str is immutable and thus should use __new__ instead of __init__. >>> class bob(str): ... def __new__(self, fred=3): ... self.fred=fred ... return self ... >>> george=bob() >>> george.fred 3 >>> george=bob(fred=7) >>> george.fred 7 Don't have a chance to read it now but maybe pep 253 explains it. http://www.python.org/dev/peps/pep-0253/ Chris
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